Shorter walk test durations to detect ambulatory oxygen desaturation in interstitial lung disease: an observational cohort study.

INTRODUCTION

The 6-min walk test (6MWT) oxygen desaturation is an indication for ambulatory oxygen therapy (British Thoracic Society (BTS), peripheral oxygen saturation ( ) <90%; American Thoracic Society (ATS), ≤88%). Shorter walk test durations may be beneficial in remote monitoring or in severe interstitial lung disease (ILD), where completing a 6MWT is challenging.

METHODS

Retrospective routine clinical 6MWT with minute interval , lung function and mortality data were collected from patients with ILD. Median lowest at different time periods of the 6MWT were compared statistically and prognostically. Patients were classified by the Distance-Oxygen-Gender-Age-Physiology (DO-GAP) index.

RESULTS

274 patient records were analysed. The median values recorded at 0-1, 1-2, 2-3, 3-4, 4-5 and 5-6 min of the 6MWT were 96%, 93%, 92%, 92%, 91.5% and 91%, respectively (p<0.001). Prognostically, the areas under the curve (AUC) for predicting 3-year mortality were significant (p<0.001) and similar for the minimum between 0-1, 1-2, 2-3, 3-4, 4-5 and 5-6 min (AUC 0.71, 0.76, 0.77, 0.76, 0.77 and 0.76, respectively). 111 patients desaturated to <90% (BTS criteria) during the 6MWT, with the median time to desaturation ranging from 1.5-2.5 min between DO-GAP groups (p=0.01). 94 patients desaturated to ≤88% (ATS criteria) during the 6MWT, with the median time to desaturation ranging from 1.5-2.2 min between DO-GAP groups.

CONCLUSION

Exertional desaturation manifests during earlier stages of the 6MWT. A 3-min walk has 87-91% sensitivity in detecting oxygen desaturation requiring ambulatory oxygen therapy, while retaining prognostic value. Shorter walk durations can efficiently detect desaturation in ILD, making it more patient-centred and feasible for remote testing.